Power-Efficient Data Modulation for All-Mechanical ULF/VLF Transmitters

Abstract

Miniaturized and power-efficient ULF/VLF (0.330 kHz) transmitters are desirable for underground and undersea wireless communications. Transmitters based on rotating permanently-polarized dipoles are promising for such applications. This paper proposes a power-efficient data modulation scheme for such mechanical transmitters based on continuous-frequency FSK (CF-FSK). Theoretical analysis and simulations show that 8-ary CF-FSK is optimal since it minimizes average mechanical torque for a given bit rate. Model predictive control (MPC) of a permanent magnet (PM) motor is proposed for robust implementation of the data modulation scheme. Preliminary results from an experimental prototype are also presented.